Strip Test For Rapid Detection Research Articles

Modified streptavidin–biotin based lateral flow test strip for rapid detection of SARS-CoV-2 S1 antigen in saliva samples

Compared to other infectious diseases, for which LFT development can take years, SARS-CoV-2 antigen LFTS were developed and deployed within months. LFTS for antigen detection were adopted on an unprecedented scale during the COVID-19 pandemic, but many of them lack the sensitivity especially for samples with low viral load. In our previous work, we developed an enhanced signal strip for detection of SARS CoV-2 SI antigens in saliva. Here we introduce some modification to improve the sensitivity, and specificity, and to lower the cost of the strip, by using biotin streptavidin (BS) system. In the modified BS strip, gold-streptavidin and biotinylated Nanobodies (Nbs) against S1 antigen were externally mixed with the tested samples (saliva or nasopharyngeal swab) before their application on the sample pad of the test strip containing angiotensin converting enzyme (ACE-2), as the capturing probe. The study included 320 individuals, with 180 being positively confirmed by RT-PCR and 140 confirmed negative, as well as, 45 health care workers, who were responsible for screening and handling of surgical cases in General Surgery Department and COVID clinic of TBRI. Our results proved that modified BS strip improved the overall sensitivity and specificity of S1antigen detection in saliva samples (95.21% and 99.29% respectively) compared to our previously developed enhanced LFTS (91.66% and 98.57% respectively). Also, the sensitivity of cases with Ct ≤ 30, Ct ≤\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\le$$\\end{document} 35, and Ct ≤\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\le$$\\end{document} 40 using the modified BS strip showed higher values (98.54%, 95.38%, and 88.89% respectively), compared to the corresponding results of our previously developed enhanced LFTS (95.86%, 92.31%, and 82.22% respectively). There were no cross-reactions with either Middle East respiratory syndrome corona virus MERS-CoV or SARS-CoV antigens. Furthermore, we found that the lower viral detection limit (LVD) of BS strip was obviously lower than our previous LVD limit of the enhanced LFTS (0.2 × 104 copies/ml vs. 0.4 × 104 copies/ml, respectively). Our developed BS strip showed that saliva samples gave better results than nasopharyngeal swabs of the same patients. The fact of using smaller amounts of Nbs, and ACE2, as well as the dispensing off of conjugate pad when applying BS strip modifications, justified the expected reduction in the costs of the strip. The implementation of BS strips on saliva samples of 45 health co-workers, who were tested 4 and 6 days after exposure to infection, showed an increase in the sensitivity, starting from the 4th day and reaching its highest level on the 6th day in both high risk and paramedic groups (90.9%, and 80.0%, respectively). This study provides evidence that employment of the modified BS system could increase the sensitivity of the strips, lower their cost, and render them an effective screening tool for early detection of the virus in saliva of suspected Covid-19 patients.

A fluorescent probe with large Stokes for rapid detection of ammonia based on BINOL

Ammonia is a common toxic gas in industrial and agricultural production, which will cause harm to the environment and human health in certain extent. Here, a novel fluorescent probe (R)-1 based on 1,1′-binaphthol (BINOL) was synthesized for real-time, on-site and quantitative detection of ammonia. The mechanism study shows that the functional groups of –CHO and –OH on (R)-1 interact with ammonia, which changes the electronic state of the probe molecule and excites strong fluorescence. A test strip for rapid detection of ammonia was developed, which changed from light yellow to reddish brown under natural light after interacting with ammonia, thus realizing the rapid detection and easy visualization of ammonia. Meanwhile, bioimaging experiments shows that probe (R)-1 can detect exogenous ammonia in cells.

Development and characterization of a lateral flow immunochromatographic assay test strip for rapid detection of rubella virus antigen

Rubella is still considered a dangerous infectious disease, especially for pregnant women. The symptoms of rubella can be similar to those of other illnesses. Therefore, an early and accurate diagnosis of the rubella virus will help doctors make a reasonable treatment plan. This study presents the development and characterization of a novel lateral flow immunochromatographic assay test strip for rapid recognition of rubella virus antigen. Rabbit polyclonal antibodies against the rubella virus were purified with a purity of 95%. Optimal conditions for the production of the main components of a test strip were determined. Anti-rubella virus polyclonal antibodies were physically adsorbed onto the star-shaped gold nanoparticles at the optimal concentration of 1.0 μg/ml at 25°C for 30 min. The amounts of antibody per conjugate pad and immobilized on the test line were 0.2 μg/pad and 4.5 μg/cm, respectively. The properties of the test strip were characterized by testing mock clinical specimens. Reproducibility and repeatability were achieved at 100%. The limit of detection of the test strip was determined to be as low as 5 × 105 virus particles/mL. The test strip did not cross-react with six different potential interfering pathogens. The sensitivity and specificity of the test strip were determined by testing with 400 mock clinical samples and reached 99.5% and 98.5%, respectively. The Kappa statistics (k coefficient = 0.98) showed very good agreement between the generated test strip and real-time PCR results. According to the findings, the test strip can be used as an additional rapid test tool for the detection of the rubella virus.

Food safety and quality training: The use of a lateral flow immunochromatographic strip test for rapid detection of pesticide residue on leafy vegetables

Ensuring the safety and quality of leafy vegetables, especially by controlling any traces of pesticides, is crucial for maintaining human health. This international community service program was designed to expand the vocational knowledge and skills of the people of Timor-Leste in using lateral flow immunochromatographic strip tests for quickly detecting pesticide residue on leafy vegetables. The program was organized by UAD in partnership with PCIM Timor-Leste and the An-Nur Islamic Foundation. The program included several stages, including preparation, coordination, consolidation, implementation, monitoring, and evaluation. The participants’ knowledge of food safety and food hygiene increased significantly from 52% prior to training to 96% after the training. Moreover, the ability to detect pesticide contamination in vegetables using LFI technology improved by 84%, rising from just 8% before training to 92% after training. All participants expressed interest in the UAD in Timor-Leste's future continuation of this training program.

Gold conjugated nanobodies in a signal-enhanced lateral flow test strip for rapid detection of SARS-CoV-2 S1 antigen in saliva samples

Despite the transfer of COVID-19 from the pandemic to control, we are still in a state of uncertainty about long-term success. Therefore, there is a great need for rapid and sensitive diagnostics to sustain the control status. After several optimization trials, we developed lateral flow test (LFT) strips for rapid detection of SARS-CoV-2 spike 1 (S1) antigen in saliva samples. For signal enhancement of our developed strips, we applied dual gold conjugates. Gold-labeled anti-S1 nanobodies (Nbs) were employed as S1 detector conjugate, while gold-labeled angiotensin-converting enzyme 2 (ACE2) was used as S1 capturing conjugate. In a parallel strip design, we used an anti-S1 monoclonal antibody (mAb) as an antigen detector instead of anti-S1 Nbs. Saliva samples were collected from 320 symptomatic subjects (180 RT-PCR confirmed positive cases and 140 confirmed negative cases) and were tested with the developed strips. In early detection for positive samples with cycle threshold (Ct ≤ 30), Nbs-based LFT strips showed higher sensitivity (97.14%) and specificity (98.57%) than mAb-based strips which gave 90.04% sensitivity and 97.86% specificity. Moreover, the limit of detection (LoD) for virus particles was lower for Nbs-based LFT (0.4 × 104 copies/ml) than for the mAb-based test (1.6 × 104 copies/ml). Our results are in favor of the use of dual gold Nbs and ACE2 conjugates in LFT strips. These signal-enhanced strips offer a sensitive diagnostic tool for rapid screening of SARS-CoV-2 S1 antigen in the easily collected saliva samples.

Acrylate-guided chemoselective fluorescent detection of arginine and lysine in aqueous media

Arginine (Arg) and lysine (Lys), as two important essential amino acids, are widely used in many fields. Here, a novel fluorescent probe (R)-3 based on 1,1′-binaphthol (BINOL) was synthesized and it could chemoselectively detect Arg and Lys by complexing with zinc ions. The response time of each amino acid only need 1 min. The detection limit of the probe for D-/L-Arg were 60 nM and 123 nM, respectively, and the detection limit for Lys was 53 nM. Mechanistic studies revealed that the chemoselectivity comes from the selective 1,4-Michael addition to the acrylate group of the probe. The probe advantaged in low detection limit, high sensitivity, chemoselectivity and that the fluorescent detection proceeded in aqueous phase. A test strip for rapid detection of arginine was prepared, which gave yellowish color to Arg under natural light and bright yellow to Arg under 254 nm ultraviolet light. The test strip allows rapid detection and easy visualization for Arg.

Utilization of a lateral flow colloidal gold immunoassay strip based on surface-enhanced Raman spectroscopy for rapid detection of glycinin

Glycinin is an important storage protein in soybean, but it can also lead to allergic reactions in humans. In this study, based on a low-cost, simple, rapid and portable lateral flow immunoassay test strip, combined with high sensitivity surface enhanced Raman spectroscopy (SERS) technology, a sandwich lateral flow immunochromatographic test strip for rapid detection of soybean allergen glycinin is established. In the experiment, colloidal gold was covalently conjugated with rabbit-derived polyclonal antibodies of glycinin and Raman probe molecule 4-aminothiophenol(4-PATP) to prepare the immunoprobe. The respective optimal PATP and optimal antibody labeling amounts of colloidal gold solution were 1.05 × 10-2mol/L and 4.6 × 10-8mol/L. The detection limit of the test strip for glycinin was 4.87 ng/mL. The recovery rate ranged from 91 to 107 % and the CV was between 3 and 10 %. The test strip underwent no cross-reaction with β-conglycinin, sesame protein, peanut protein, wheat protein or whey protein. The results of the experiment showed that this method exhibits high sensitivity and specificity.

Development of an immunochromatographic strip test for rapid detection of a potent neutralizing anti-interferon gamma antibody in adult-onset immunodeficiency.

Adult-onset immunodeficiency (AOID) is associated with the presence of anti-interferon gamma autoantibodies (anti-IFN-γ autoAbs), which neutralizes IFN-γ signaling and leads to susceptibility to intracellular opportunistic infections. However, measuring neutralizing autoAbs is not practical for general clinical laboratories. This study aims to develop a competitive immunochromatographic (IC) strip test for detecting autoAbs that recognize the same epitope as a potent neutralizing antibody. The competitive IC strip test detecting autoAbs that recognize the same epitope as mouse anti-IFN-γ monoclonal antibody, clone B27 (B27 mAb) was fabricated and used to determine B27 epitope recognizing autoAb (B27 AAb) in AOID plasma. The competitive ELISA was used as a comparative method. AR patients. The efficacy of the IC strip test was compared with competitive ELISA and found a percent positive agreement of 91.30%, a percent negative agreement of 79.31%, and a percent overall agreement of 84.62%. The results from the competitive IC strip test were consistent with those from competitive ELISA, indicating that the generated IC strip could detect B27 AAb in AOID plasma.

Functional nucleic acid lateral flow magnetic biosensor based on blocking the super PCR and magnetic test strip for rapid detection of genetically modified maize MON810†

Although PCR is a typical temperature-variable amplification technique for nucleic acids, it still faces challenges in rapid screening, such as low speed, poor sensitivity, inferior visualization, and weak stability. In this paper, a universal functional nucleic acid (FNA) lateral flow magnetic biosensor was constructed using blocking super PCR (BS-PCR) and a magnetic test strip (MTS). In theory, the visualized and magnetic output of dsDNA-based amplicons were achieved via ssDNA/dsDNA conversion by blocking linkers in the PCR primers and magnetic probes. In application, high-speed, super-sensitive, highly stable rapid screening was realized by taking advantage of the speediness of the super PCR reactor and the anti-background interference, visualization and high stability of magnetic signal readout. The genetically modified maize MON810 was selected as a double-stranded model target, while 5-min BS-PCR and 5-min magnetic signal readouts achieved the screening results within 10 min. Furthermore, the exponential PCR amplification and magnetic-based sensibilization improved the sensitivity to a single copy. This biosensor is simple and portable, with significant potential for rapid on-site screening.

A wearable AIEgen-based lateral flow test strip for rapid detection of SARS-CoV-2 RBD protein and N protein

Accurate and rapid detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is significant for early tracing, isolation, and treatment of infected individuals, which will efficiently prevent large-scale transmission of coronavirus disease 2019 (COVID-19). Here, two kinds of test strips for receptor binding domain (RBD) and N antigens of SARS-CoV-2 are established with high sensitivity and specificity, in which AIE luminogens (AIEgens) are utilized as reporters. Because of the high brightness and resistance to quenching in aqueous solution, the limit of detection can be as low as 6.9 ng/mL for RBD protein and 7.2 ng/mL for N protein. As an antigen collector, an N95 mask equipped with a test strip with an excellent enrichment effect would efficiently simplify the sampling procedures. Compared with a test strip based on Au nanoparticles or fluorescein isothiocyanate (FITC), the AIEgen-based test strip shows high anti-interference capacity in complex biosamples. Therefore, an AIEgen-based test strip assay could be built as a promising platform for emergency use during the pandemic.

Wearable Aiegens-Based Lateral Flow Test Strip for Rapid Detection of SARS-CoV-2 N Protein and BRD Protein

\Accurate and rapid detection of SARS-CoV-2 is significant for early tracing, isolating and treating the infected patients, which will efficiently prevent the virus large-scale spread from human to human. In this paper, two kinds of novel quantitative lateral flow test strip for N and RBD antigens of SARS-CoV-2 were established with high sensitivity, which utilize AIE luminogens (AIEgens) as reporter. Because of the high brightness and resistance of quenching property in aqueous of the AIEgens, the limit of detection of 7.2 ng/mL for N protein and 6.9 ng/mL for RBD protein could be achieved with the AIEgens-based lateral flow test strip. Furthermore, it was negative for other protein or antigen samples assay, which demonstrated the great specificity of the test strategy. A N95 mask equipped with the test strip was designed to employ as the antigen collector with excellent enrichment effect. Compared with the other two test strips based on the Au nanoparticle and FITC, the well-designed AIEgens-based lateral flow test strip presented high sensitivity and excellent anti-interference capacity in complex bio-samples. Furthermore, the AIEgens-based lateral flow test strip assay could be built as a promising platform for the emergency usage at pandemic.Funding: This work was supported by the NSFC (51961160730, 51873092, and 81921004), the National Key R&D Program of China (Intergovernmental Cooperation Project, 2017YFE0132200), the Fundamental Research Funds for the Central Universities, and the Tianjin Science Fund for Distinguished Young Scholars (19JCJQJC61200).Declaration of Interests: The authors declare no competing interests.

Development of novel-nanobody-based lateral-flow immunochromatographic strip test for rapid detection of recombinant human interferon α2b

Recombinant human interferon α2b (rhIFNα2b) is widely used as an antiviral therapy agent for the treatment of hepatitis B and hepatitis C. The current identification test for rhIFNα2b is complex. In this study, an anti-rhIFNα2b nanobody was discovered and used for the development of a rapid lateral flow strip for the identification of rhIFNα2b. RhIFNα2b was used to immunize an alpaca, which established a phage nanobody library. After five steps of enrichment, the nanobody I22, which specifically bound rhIFNα2b, was isolated and inserted into the prokaryotic expression vector pET28a. After subsequent purification, the physicochemical properties of the nanobody were determined. A semiquantitative detection and rapid identification assay of rhIFNα2b was developed using this novel nanobody. To develop a rapid test, the nanobody I22 was coupled with a colloidal gold to produce lateral-flow test strips. The developed rhIFNα2b detection assay had a limit of detection of 1 μg/mL. The isolation of I22 and successful construction of a lateral-flow immunochromatographic test strip demonstrated the feasibility of performing ligand-binding assays on a lateral-flow test strip using recombinant protein products. The principle of this novel assay is generally applicable for the rapid testing of other commercial products, with a great potential for routine use in detecting counterfeit recombinant protein products.

Development of colloidal gold-based test strip for rapid detection of serotype 4 fowl adenovirus

The outbreaks of hepatitis-hydropericardium syndrome (HPS) caused by serotype 4 fowl adenovirus (FAdV-4) have spread from broilers to laying hens, breeders, geese and Cherry Valley duck, resulting in high economic losses to the poultry industry globally. In this study, a rapid colloidal gold test strip for detection of FAdV-4 was developed by using two monoclonal antibodies (mAbs) against the Fiber-2 of FAdV-4. Specificity analysis revealed that the test strip only reacted with FAdV-4, but not with other pathogens including different serotypes of fowl adenovirus and other avian pathogens tested. The limit of the detection (LOD) of the strip could reach as low as 0.1 μg/0.1 mL of GST-Fiber-2 protein and 1 × 105 TCID50/0.1 mL of FAdV-4, respectively. Moreover, the test strip could be efficiently applied in detecting tissue samples from diseased chickens with HPS. Comparison analysis further revealed that the test strip showed good compatibility with PCR assay for detection of virus isolates and clinical samples. In conclusion, our test strip provides an efficient on-site diagnostic method in a quick and convenient manner for detection of FAdV-4, especially in resource-limited areas.

Development of Recombinase Aided Amplification Combined With Disposable Nucleic Acid Test Strip for Rapid Detection of Porcine Circovirus Type 2.

Porcine circovirus type 2 (PCV2) is the dominant causative agent of PCV2 systemic disease (PCV2-SD) in pigs. It can also associate with other diseases such as respiratory and enteric diseases, reproductive failure, porcine dermatitis and nephropathy syndrome in pigs. Currently, PCV2 infection is a considerable threat in the swine industry. Therefore, it is of great significance to prevent, control, and accurately detect PCV2 in pig farms. Recombinase aided amplification (RAA) technology is an isothermal nucleic acid amplification technology that could rapidly amplify the target gene fragment at a constant temperature. The amplification products labeled with specific molecules could be visually detected using the test strip with the corresponding antibody. In the present study, the RAA technology combined with a nucleic acid test strip (RAA-strip) was established for simple and specific detection of PCV2. Primers and probes targeting the PCV2 ORF2 gene were designed according to the RAA technology principles. The PCV2 RAA-strip established in this study could detect as low as 103 copies/μL of recombinant plasmids containing the PCV2 ORF2 gene fragment. The lowest detection limit about viral DNA and virus titers was 6.7 × 10−6 ng/μL and 10 TCID50/mL, respectively. Furthermore, no cross-reaction with other porcine viruses occurred at 37°C and within 15 min. We used 42 clinical samples to assess the performance of our established method. The positive rate of clinical samples detected by PCV2 RAA-strip was 50.00%. This was similar to that detected by PCV2 PCR (45.24%). In conclusion, due to the advantages of strong specificity, high sensitivity, excellent reproducibility, and simple operation method, our PCV2 RAA-strip is suitable for the rapid clinical detection of PCV2 on-site.

Development and evaluation of a convenient immunochromatographic strip test for rapid detection of cyprinid herpesvirus 2 (CyHV-2).

Cyprinid herpesvirus 2 (CyHV-2) has become a serious threat to the gibel carp Carassius auratus gibelio industry and has led to enormous losses worldwide. We have therefore developed an immunochromatographic strip (ICS) to enable rapid on-site detection of CyHV-2 by aquaculture facility staff. The ICS employs 2 monoclonal antibodies (MAbs 2C3-1E6 and 3H2-1G5) against the ORF25 protein, a CyHV-2 membrane protein, as the capture and detection antibodies, respectively. Indirect immunofluorescence assay (IIFA) and Western blotting of CyHV-2-infected fathead minnow cells indicated that the 2 MAbs could specifically bind CyHV-2 by recognizing ORF25 antigen. Sandwich ELISA showed that the detection limit of ORF25 protein halved when MAb 2C3-1E6 served as the capture antibody compared to MAb 3H2-1G5. The test for detecting purified CyHV-2 using the ICS could be completed in 10 min and the sensitivity was 1 µg ml-1. Sensitivity of the ICS remained stable following storage at 4, 25 and 37°C for 6 mo. Tissue homogenate from gibel carp with and without obvious gill hemorrhages was subjected to CyHV-2 detection using the ICS: the results were in good accordance with conventional PCR. Our ICS does not require highly trained technicians or specialized equipment, making it suitable for rapid diagnosis of CyHV-2 infection both in the laboratory and in the field.

A colloidal gold test strip assay for the detection of African swine fever virus based on two monoclonal antibodies against P30.

African swine fever (ASF), caused by African swine fever virus (ASFV), was first reported in Kenya in 1921, but an effective vaccine or antiviral drug is still not available for ASFV control. Rapid and effective diagnostics are key steps in managing ASF. We generated two monoclonal antibodies (MAbs) against the ASFV phosphoprotein P30 and designated these as 3H7A7 and 6H9A10. Epitope mapping revealed that MAb 3H7A7 and 6H9A10 recognized aa 144-154 and aa 12-18 of P30, respectively. A signal-amplified sandwich colloidal gold test strip for rapid detection of ASFV was developed based using these MAbs. Sensitivity and specificity analysis showed that the detection limit of the strip was 2.16 ng of P30. The strip only reacted with ASFV and did not react with other common porcine viruses. In detection tests using 153 clinical field samples including sera, plasma, anticoagulant-treated blood, and tissue, the strip had 95.42% concordance with real-time PCR. The new MAbs specific for P30 and the rapid colloidal gold test strip helped to reveal novel B cell epitopes in P30 and provide an efficient diagnostic test for on-site clinical detection of ASF.

Nanogold‐based immunochromatographic strip test for rapid detection of clinical and environmental strains of Vibrio cholerae

AbstractA nanogold‐based immunochromatographic strip test (VCG strip test) for the detection of all 70 isolates of Vibrio cholerae including O1, O139, and non‐O1/O139 (NVCs) was developed using two monoclonal antibodies (MAbs), namely VC‐63 and VC‐201, which bound specifically to 10 and 15 kDa proteins. Direct detection of V. cholerae in experimentally spiked fresh seafood samples such as shrimp, blood clam, mussel, and oyster could be achieved with sensitivities of 107 CFU/ml, which was similar to that of the dot blotting test using each MAb. The detection sensitivity could be improved to 103 or 10 or 1 CFU/ml of original bacterial content after preincubation of the sample in alkaline peptone water for 6, 12, and 24 hr consecutively. However, the detection sensitivities were also dependent on the content of other bacteria in the sample that might compete or inhibit the growth of V. cholerae during the preenrichment step. Due to its broad specificity, simplicity and rapid result generation, the VCG strip test can be used for the preliminary detection of V. cholerae at point of care for both environmental and clinical strains to assist appropriate decision or epidemiological surveillance of virulent V. cholerae strains (including NVC strains), which are ubiquitous in the environment and seafood.

Development and validation of an immunochromatography test strip for rapid detection of pyrimethanil residues

ABSTRACT Pyrimethanil is one of anilinopyrimidine fungicides widely used in crop protection and frequently found in a variety of crops, including fruits, vegetables, and cereals. This paper describes the development of the first reported immunochromatography test strip (ICTS) based on colloidal gold-labeled monoclonal antibody for the detection of pyrimethanil. Under optimal conditions, the visual cut-off value of ICTS for pyrimethanil was 40 ng/mL. Using a portable strip reader, the 50% inhibition concentration and calculated LOD of pyrimethanil in the PBS samples were 4.8 and 0.9 ng/mL, respectively. When used to analyse fortified samples of fruit and vegetable, acceptable recovery rates of 83.3–105.7% with the coefficient of variation values below 11.7% were obtained. Analysis of blindly fortified samples by the proposed ICTS gave similar results to those of the ic-ELISA and HPLC-MS/MS methods. These results indicate the proposed ICTS is a rapid, simple analytical method for quantitative on-site monitoring of pyrimethanil in foodstuffs.

Development of an immunochromatographic strip test for rapid detection of sodium nifurstyrenate in fish

ABSTRACT A rapid, specific and sensitive method based an immunochromatographic strip test has been developed for the determination of sodium nifurstyrenate (NFS) residues in fish. Sample preparation procedure includes ultrasonic bath extraction with acetonitrile, sample centrifugation at 8000 rpm for 10 min, filtration through the 0.22 µm membrane filter, and drying over nitrogen (60°C) and res-suspension. The antigen (NFS-ovalbumin) and a goat anti-mouse IgG antibody were drawn onto a nitrocellulose membrane as the test line and control line, respectively. Under optimized conditions, the NFS cut-off limits for test strips was determined as 5 ng/mL in 0.01 M phosphate buffered saline and 10 ng/mL in fish. Results were obtained within 5 min. Our data suggests this immunochromatographic assay can be used for the sensitive, rapid, and specific on-site screening for NFS in fish.

Quantum Dot-Labeled Immunochromatographic Test Strip for Rapid Detection of Ochratoxin A in Cereals

Objective:A quantum dot-labeled immunochromatographic test strip for the determination of ochratoxin A(OTA)in cereals was developed based on the competitive inhibition principle. Methods:Quantum dot antibody conjugates(QD-Ab)were prepared by coupling an carboxy-functionalized quantum dot(QD)with an ochratoxin A polyclonal antibody(Antibody,Ab)via the activated ester method;Different amounts of QD-Ab and working fluid were used to optimize the working conditions of the quantum dot-labeled immunochromatographic test strip;The effectiveness of the method was verified by a commercial kit. Results:When the molar ratio of QD to Ab was 1:10,the fluorescence characteristics of QD-Ab were the best;when QD-Ab and working fluid were added at 1,10 μL,respectively,the best results of quantum dot-labeled immunochromatographic test strips were obtained;The detection limit of the quantum dot-labeled immunochromatographic test strip in the assay buffer was 0.5 μg/L,and the detection limit of OTA in the cereal sample was 5 μg/kg,the entire detection process could be completed within 10 min;The quantum dot-labeled immunochromatographic test strip had good specificity and effectiveness. Conclusion:This assay is simple,rapid,and sensitivity. It can meet the requirements of on-site rapid detection of ochratoxin A in cereals.